Method of manufacturing multi-layer electrode for a capacitive pressure sensor and multi-layer electrodes formed therefrom

ABSTRACT

A multi-layer electrode for a capacitive pressure sensor is manufactured according to a method including co-extruding a conductive polymer layer and a dielectric foam layer and forming coextruded layers of the capacitive pressure sensor and pressure rolling an XY layer and the coextruded layers together and forming the multi-layer electrode.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. Pat. Application No.16/950,547, filed on Nov. 17, 2020, and titled “METHOD OF MANUFACTURINGMULTI-LAYER ELECTRODE FOR A CAPACITIVE PRESSURE SENSOR AND MULTI-LAYERELECTRODES FORMED THEREFROM.” The disclosure of the above application isincorporated herein by reference.

FIELD

The present disclosure relates to manufacturing multi-layer electrodesand particularly to low cost manufacturing multi-layer electrodes.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

Electrical switches are commonly used to “turn on”, “turn off”, and/orregulate functions and operations of machines. For example, switches forradio control, audio volume control, heating and/or air conditioningcontrol, cruise control, among others, are typically included and placedor located on a steering wheel of a vehicle such that a driver can reachthe switches without removing their hands from the steering wheel. Inaddition, some, if not most, of the electronic switches are pressureactivated, i.e., are activated by pressure applied by the driver.

The present disclosure addresses issues related to pressure activatedswitches and other issues related to manufacturing of pressure activatedswitches.

SUMMARY

This section provides a general summary of the disclosure and is not acomprehensive disclosure of its full scope or all of its features.

In one form of the present disclosure, a multi-layer electrode for acapacitive sensor includes an XY layer including a conductive layerprinted onto a polymer layer and coextruded layers of a conductivepolymer layer and a dielectric foam layer. The dielectric foam layer isdisposed adjacent to the conductive layer of the XY layer.

In variations of this form of the present disclosure, which may beimplemented individually or in any combination: the conductive layerincludes a conductive ink layer; the conductive ink layer has athickness between about 10 µm to about 100 µm; the conductive ink layerincludes at least one of silver, graphene, carbon, and indium tin oxide;the conductive polymer layer includes polyethylene terephthalate (PET);the PET is recycled PET; the conductive polymer layer includes a filler;the filler includes graphene and carbon nanostructures; the carbonnanostructures include carbon nanotubes; the conductive polymer layerincludes between about 2 wt.% to about 15 wt.% of the graphene andbetween about 0.01 wt.% and 5 wt.% of the carbon nanotubes; theconductive polymer layer has a flexural modulus equal to or greater than5,000 MPa; the conductive polymer layer has an electrical resistivityless than or equal to 10 Ohm/mm³; the conductive polymer layer has aflexural modulus equal to or greater than 5,000 MPa and an electricalresistivity less than or equal to 10 Ohm/mm³; the conductive polymerlayer includes between about 2 wt.% to about 15 wt.% of graphene,between about 0.01 wt.% and 5 wt.% of carbon nanotubes, a flexuralmodulus equal to or greater than 5,000 MPa and an electrical resistivityless than or equal to 10 Ohm/mm³; and the conductive polymer layerincludes between about 8 wt.% to about 10 wt.% of the graphene andbetween about 0.01 wt.% and 1 wt.% of the carbon nanotubes.

In another form of the present disclosure, a multi-layer electrode for acapacitive pressure sensor includes a conductive polymer layer, adielectric foam layer contacting the conductive polymer layer, and an XYlayer including conductive ink roll to roll rotogravure printed onto apolymer layer. The XY layer contacts the dielectric foam layer, and thedielectric foam layer disposed between the XY layer and the conductivepolymer layer.

In variations of this form of the present disclosure, which may beimplemented individually or in any combination: the conductive polymerlayer includes between about 2 wt.% to about 15 wt.% of graphene,between about 0.01 wt.% and 5 wt.% of carbon nanotubes; and theconductive polymer layer has a flexural modulus equal to or greater than5,000 MPa and an electrical resistivity less than or equal to 10Ohm/mm³.

In yet another form of the present disclosure, a method of manufacturinga multi-layer electrode for a capacitive pressure sensor includesco-extruding a conductive polymer layer and a dielectric foam layer andforming coextruded layers of the capacitive pressure sensor, andpressure rolling an XY layer and the coextruded layers together andforming the multi-layer electrode.

In variations of this form of the present disclosure, the conductivepolymer layer has a flexural modulus equal to or greater than 5,000 MPaand an electrical resistivity less than or equal to 10 Ohm/mm³.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

DRAWINGS

In order that the disclosure may be well understood, there will now bedescribed various forms thereof, given by way of example, referencebeing made to the accompanying drawings, in which:

FIG. 1 is side view of a roll to roll printer forming a mutualcapacitance sensor layer of a multi-layer electrode according to theteachings of the present disclosure;

FIG. 2 is a top view of the mutual capacitance sensor layer formed inFIG. 1 with a conductive ink layer printed on a polymer layer;

FIG. 3A is a view of section 3A-3A in FIG. 2 ;

FIG. 3B is a view of section 3B-3B in FIG. 2 ;

FIG. 4 is a side view of a co-extrusion machine and a press rollerforming a multi-layer electrode according to the teachings of thepresent disclosure;

FIG. 5A is a side cross-sectional view of the multi-layer electrode inFIG. 4 according to one variation of the present disclosure;

FIG. 5B is a side cross-sectional view of the multi-layer electrode inin FIG. 4 according to another variation of the present disclosure; and

FIG. 6 is a flow chart of a method of forming a multi-layer electrodefor a capacitive pressure sensor according to the teachings of thepresent disclosure.

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses. Itshould be understood that throughout the drawings, correspondingreference numerals indicate like or corresponding parts and features.

Referring to FIG. 1 , a step for manufacturing a multi-layer electrodefor a capacitive pressure sensor using a printer 10 is shown. Theprinter 10 includes a first roller 100, a second roller 110 and an inkcontainer 120 with an electrically conductive ink 122 (referred toherein simply as “conductive ink”). In some variations of the presentdisclosure, the printer 10 is a rotogravure printer 10, the first roller100 is an impression roller 100, and the second roller 110 is a platecylinder 110 with a plate 112 having cells 114. As shown in FIG. 1 , theplate cylinder 110 rotates such that the cells 114 pass through and arefilled with the conductive ink 122, and then come into contact with aprint surface 142 of a polymer film (layer) 140 moving between theimpression roller 100 and the plate 112 such that the conductive ink 122is transferred to the print surface 142. In at least one variation, awiper 124 (also known as a doctor blade) is included and removes excessconductive ink 122 from the plate 112 and the cells 114 before the cells114 reach the polymer layer 140.

In some variations, the polymer layer 140 is provided from a feed roller130 and then gathered or rolled onto a take-up roller 150. That is, insome variations the printer 10 is a roll to roll printer. In addition,the conductive ink 122 dries and forms a plurality of conductive inklayers 122 a on the polymer layer 140 before and/or during being rolledonto the take-up roller 150. The sections or areas of the polymer layer140 with the conductive ink layers 122 a form a plurality of mutualcapacitance sensor layers 160 (FIG. 2 ) of a multi-layer electrodedescribed in greater detail below. As used herein, the term or phrase“mutual capacitance sensor layer” refers to a capacitance sensor layerwith a planar construction such that the electrodes and traces for thesensor layer are fabricated on the same plane of insulating substratematerial.

Non-limiting examples of the polymer layer 140 include polymer layers(e.g., polymer sheet or film) made from polyethylene (PE), polyethyleneterephthalate (PET), polytetrafluoroethylene (PTFE), and polyvinylchloride (PVC), polypropylene (PP), polyamide (PA), among others. Insome variations the polymer layer 140 is made from recycled polymermaterial(s). Also, in some variations the polymer layer 140 has athickness between about 0.25 mm to about 10 mm, for example betweenabout 0.4 mm to about 7.5 mm, or between about 0.5 mm to about 6 mm.

Also, non-limiting examples of conductive ink 122 include silver inks,nano-silver inks, copper inks, carbon nanotube inks, carbon/grapheneinks, indium tin oxide (ITO) inks, and conductive polymer inks, amongothers. In some variations the conductive ink includes a solvent and/orsuch as but not limited to ethanol, an ethyl solvent, methanol, a methylsolvent, among others. And in at least one variation, the conductive inklayer has a thickness between about 5 micrometers (µm) and about 100 µm,for example, between about 5 µm and about 50 µm, between about 7.5 µmand about 30 µm, or between about 10 µm and about 20 µm.

Referring to FIGS. 3A-3B, in some variations the conductive ink layer122 a is disposed directly onto the polymer layer 140 to form a mutualcapacitance sensor layer 160 a as shown in FIG. 3A, while in othervariations at least one additional layer 125 (referred to hereaftersimply as “additional layer 125”) is disposed between the conductive inklayer 122 a and the polymer layer 140 as shown in FIG. 3B. For example,in some variations the polymer layer 140 is a transparent or translucentpolymer layer and the additional layer 125 is one or more decorativelayers (e.g., an additional ink layer(s)) such that an image or color isvisible through the polymer layer 140 (e.g., when viewing from the -zdirection).

Referring to FIG. 4 , another step for manufacturing the multi-layerelectrode is shown where a co-extrusion machine 20 with a first extruder210 and a second extruder 220 is used to form a co-extruded layer 170with a conductive polymer layer 172 (FIGS. 5A-5B) and a dielectric layer174. In some variations, the first extruder 210 is configured to extrudethe conductive polymer layer 172 (FIGS. 5A-5B) and the second extruder220 is configured to extrude the dielectric layer 174. In othervariations, the first extruder 210 is configured to extrude dielectriclayer 174 and the second extruder 220 configured to extrude theconductive polymer layer 172. And in some variations, the dielectriclayer 174 is a dielectric foam layer.

As shown in FIG. 4 , the first extruder 210 extrudes material for theconductive polymer layer 172 and the second extruder 220 extrudesmaterial for the dielectric layer 174 to a multi-manifold 230 andthrough a T-die 240 to form the co-extruded layer 170. It should beunderstood that the extrusion temperature or range of extrusiontemperatures for the conductive polymer layer 172 and the dielectriclayer 174 will vary and be a function of material supplierrecommendations and/or melting temperature of the material. In additionthe extrusion temperature can vary throughout the various zones of thefirst extruder 210 and the second extruder 220. For example, in onenon-limiting example the first extruder 210 and the second extruder 220(referred to herein collectively as “extruders 210, 220”) each have arear zone (not shown) where material is dropped into the extruders 210,220, one or more middle zones (not shown) where material is melted andmixes, a front zone (not shown) where temperature of the melted materialis stabilized, and an extension and die (not shown) where theco-extruded layer 170 is formed. For example, for materials such asethylene-vinyl acetate (EVA) with a desired melting temperature of 205°F. (96° C.), an extruder or co-extruder could have a rear zone with adesired temperature of 90° F. (32° C.), a first middle zone with adesired temperature of 150° F. (66° C.), a second middle zone with adesired temperature of 205° F. (96° C.), and a front zone, extension anddie with a desired temperature of 205° F. (96° C.). And for materialssuch as polyethylene terephthalate (PET) with a desired meltingtemperature of 482° F. (250° C.), an extruder or co-extruder could havea rear zone with a desired temperature of 500° F. (260° C.), a first andsecond middle zone with a desired temperature of 518° F. (270° C.), afront zone with a desired temperature of 536° F. (280° C.), and anextension and die with a desired temperature of 554° F. (290° C.).

In some variations the conductive polymer layer 172 has a thicknessbetween about 0.2 mm to about 10.0 mm, for example between about 0.3 mmto about 6.0 mm, between 0.5 mm to about 2.5 mm, or between about 0.5 mmto about 1.0 mm.

In some variations the conductive polymer layer 172 includes one or morefillers. As used herein the term “filler” or “fillers” refers toparticles, nanoparticles, fibers, nanotubes, among others that provideor enhance a physical, mechanical and/or chemical property of theconductive polymer layer 172. For example, in some variations theconductive polymer layer 172 can include a carbon filler to enhance theelectrical and/or mechanical properties of the conductive polymer layer172. Particularly, the conductive polymer layer 172 can include betweenabout 2 weight percent (wt.%) to about 15 wt.% of graphene. In thealternative, or in addition to, the conductive polymer layer 172 caninclude between about 0.01 wt.% to about 5 wt.% carbon nanotubes. Insome variations, the conductive polymer layer 172 includes between about8 wt.% to about 10 wt.% graphene and between about 0.01 wt.% to about1.0 wt.% carbon nanotubes. One non-limiting example of the graphene isGrapheneBlack™ from Nano-xplore which is low cost multi-layer graphene(6-10 layers) and one non-limiting example of the carbon nanotubes isATHLOS™ Carbon Nanostructures (CNS) from Cabot.

Accordingly, the conductive polymer layer 172 has desired and tailoredelectrical properties. In addition, in some variations the conductivepolymer layer 172 has desired mechanical properties. For example, in atleast one variation the conductive polymer layer 172 has an electricalresistivity less than or equal to 10 Ohms per cubic millimeter (Ohm/mm³)and in some variations the conductive polymer layer 172 has a flexuralmodulus equal to or greater than 5,000 megapascals (MPa). In at leastone variation the conductive polymer layer 172 has an electricalresistivity less than or equal to 10 Ohm/mm³ and a flexural modulusequal to or greater than 5,000 MPa.

In some variations the dielectric layer 174 is a dielectric foam layerwith a thickness between about 0.2 mm to about 15 mm, for examplebetween about 0.3 mm to about 13 mm, between about 0.4 mm to about 12.5mm, or between about 0.5 mm to about 12 mm. Also, non-limiting examplesof the dielectric layer 174 include dielectric layers formed frompolyethylene, polyethylene foam, polyurethane, among others. In somevariations, the dielectric layer 174 is formed from a foamed polymersuch as but not limited to polypropylene (PP) foam, thermoplasticelastomer (TPE) foam, polyvinyl chloride (PVC) foam, thermoplasticpolyurethane (TPU) foam, thermoplastic vulcanizate (TPV) foam, amongothers.

In some variations the co-extruded layer 170 is co-extruded onto acooling roller 270. And in such variations the polymer layer 140 withthe plurality of mutual capacitance sensor layers 160 on a supply roller250 is press rolled onto the co-extruded layer 170 with a press roller260 such that a plurality of multi-layer electrodes 180 are formed. Inother variations, the first extruder 210 and the second extruder 220extrude the co-extruder layer 170 onto a separate roller (not shown) forstorage and/or additional processing before being press rolled onto themutual capacitance sensor layer 160. In addition, in at least onevariation an adhesive (not shown) is applied between the polymer layer140 with the plurality of mutual capacitance sensor layers 160 and theco-extruded layer 170 before being press rolled together such thatbonding or adhesion between the plurality of mutual capacitance sensorlayers and the co-extruded layer 170 is enhanced.

It should be understood that the plurality of multi-layer electrodes 180(i.e., the co-extruded layer 170 press rolled and bonded to the polymerlayer 140 with the plurality of mutual capacitance sensor layers 160bonded thereto) can be rolled onto another roller (not shown) forstorage and/or further processing, cut into a plurality of sheets (notshown) comprising the plurality of multi-layer electrodes 180 forstorage and/or further processing, and the like.

Referring to FIGS. 5A-5B, in some variations the co-extruded layer 170is pressed rolled onto the mutual capacitance sensor layer 160 a to forma multi-layer electrode 180 a as shown in FIG. 5A, while in othervariations the co-extruded layer 170 is pressed rolled onto the mutualcapacitance sensor layer 160 b to form a multi-layer electrode 180 b(collectively referred to herein as “multi-layer electrodes 180”) asshown on FIG. 5B. Also, and as shown in FIGS. 5A-5B, the dielectriclayer 174 is rolled onto the conductive ink layer 122 a such that thedielectric layer 174 is disposed between the conductive ink layer 122 aand the conductive polymer layer 172. Accordingly, the multi-layerelectrodes 180 are configured for use as or to be used as part of apressure sensor.

For example, when the conductive ink layer 122 a or the conductivepolymer layer 172 are electrically connected to an energy source (e.g.,a battery) a self-capacitance mode of the multi-layer electrode 180 isprovided. In the alternative, when the conductive ink layer 122 a andthe conductive polymer layer 172 are electrically connected to an energysource a mutual-capacitance mode of the multi-layer electrode 180 isprovided. In some variations the conductive ink layer 122 a is a top orouter layer and serves as a ground electrode and the conductive polymerlayer 172 is a bottom or inner layer and serves as an activatedelectrode. In such variations, pressure applied on the polymer layer 140results in squeezing of compression of the dielectric layer 174 suchthat a capacitive field proportional to the applied pressure is created.In addition, the flexural modulus of the conductive polymer layer 172provides a rigidity or stiffness for the multi-layer electrodes 180 suchthat normal or typical pressure from an individual’s hand and fingersapplied to the multi-layer electrodes 180 results in a desiredcapacitive field.

Referring to FIG. 6 , a method 30 of manufacturing the multi-layerelectrode 180 is shown. The method 30 includes roll to roll printing aconductive ink layer onto a polymer layer and forming a mutualcapacitance sensor layer at 300, co-extruding a conductive polymer layerand a dielectric layer and forming a co-extruded layer at 310, and pressrolling the mutual capacitance sensor layer and the co-extruded layertogether to form the multi-layer electrode at 320. In some variations,an adhesive (e.g., a spray adhesive) is applied between the mutualcapacitance sensor layer and the co-extruded layer at 315 before pressrolling at 320 such that adhesion between the mutual capacitance sensorlayer and co-extruded layers is enhanced.

Unless otherwise expressly indicated herein, all numerical valuesindicating mechanical/thermal properties, compositional percentages,dimensions and/or tolerances, or other characteristics are to beunderstood as modified by the word “about” or “approximately” indescribing the scope of the present disclosure. This modification isdesired for various reasons including industrial practice, material,manufacturing, and assembly tolerances, and testing capability.

As used herein, the phrase at least one of A, B, and C should beconstrued to mean a logical (A OR B OR C), using a non-exclusive logicalOR, and should not be construed to mean “at least one of A, at least oneof B, and at least one of C.”

The description of the disclosure is merely exemplary in nature and,thus, variations that do not depart from the substance of the disclosureare intended to be within the scope of the disclosure. Such variationsare not to be regarded as a departure from the spirit and scope of thedisclosure.

What is claimed is:
 1. A multi-layer electrode for a capacitive sensor,the multi-layer electrode comprising: an XY layer including a conductivelayer printed onto a polymer layer; and coextruded layers of aconductive polymer layer and a dielectric foam layer, wherein thedielectric foam layer is disposed adjacent to the conductive layer ofthe XY layer.
 2. The multi-layer electrode according to claim 1, whereinthe conductive layer includes a conductive ink layer.
 3. The multi-layerelectrode according to claim 2, wherein the conductive ink layer has athickness between about 10 µm to about 100 µm.
 4. The multi-layerelectrode according to claim 2, wherein the conductive ink layercomprises at least one of silver, graphene, carbon, and indium tinoxide.
 5. The multi-layer electrode according to claim 1, wherein theconductive polymer layer comprises polyethylene terephthalate (PET). 6.The multi-layer electrode according to claim 5, wherein the PET isrecycled PET.
 7. The multi-layer electrode according to claim 1, whereinthe conductive polymer layer comprises a filler.
 8. The multi-layerelectrode according to claim 7, wherein the filler comprises grapheneand carbon nanostructures.
 9. The multi-layer electrode according toclaim 8, wherein the carbon nanostructures comprise carbon nanotubes.10. The multi-layer electrode according to claim 9, wherein theconductive polymer layer comprises between about 2 wt.% to about 15 wt.%of the graphene and between about 0.01 wt.% and 5 wt.% of the carbonnanotubes.
 11. The multi-layer electrode according to claim 10, whereinthe conductive polymer layer has a flexural modulus equal to or greaterthan 5,000 MPa.
 12. The multi-layer electrode according to claim 10,wherein the conductive polymer layer has an electrical resistivity lessthan or equal to 10 Ohm/mm³.
 13. The multi-layer electrode according toclaim 10, wherein the conductive polymer layer has a flexural modulusequal to or greater than 5,000 MPa and an electrical resistivity lessthan or equal to 10 Ohm/mm³.
 14. The multi-layer electrode according toclaim 1, wherein the conductive polymer layer comprises between about 2wt.% to about 15 wt.% of graphene, between about 0.01 wt.% and 5 wt.% ofcarbon nanotubes, a flexural modulus equal to or greater than 5,000 MPaand an electrical resistivity less than or equal to 10 Ohm/mm³.
 15. Themulti-layer electrode according to claim 14, wherein the conductivepolym er layer comprises between about 8 wt.% to about 10 wt.% of thegraphene and between about 0.01 wt.% and 1 wt.% of the carbon nanotubes.16. A multi-layer electrode for a capacitive pressure sensor, themulti-layer electrode comprising: a conductive polymer layer; and adielectric foam layer contacting the conductive polymer layer; and an XYlayer including conductive ink roll to roll rotogravure printed onto apolymer layer, wherein the XY layer contacts the dielectric foam layer,and the dielectric foam layer disposed between the XY layer and theconductive polymer layer.
 17. The multi-layer electrode according toclaim 16, wherein the conductive polymer layer comprises between about 2wt.% to about 15 wt.% of graphene, between about 0.01 wt.% and 5 wt.% ofcarbon nanotubes.
 18. The multi-layer electrode according to claim 17,wherein the conductive polymer layer has a flexural modulus equal to orgreater than 5,000 MPa and an electrical resistivity less than or equalto 10 Ohm/mm³.
 19. A method of manufacturing a multi-layer electrode fora capacitive pressure sensor, the method comprising: co-extruding aconductive polymer layer and a dielectric foam layer and formingcoextruded layers of the capacitive pressure sensor; and pressurerolling an XY layer and the coextruded layers together and forming themulti-layer electrode.
 20. The method according to claim 19, wherein theconductive polymer layer has a flexural modulus equal to or greater than5,000 MPa and an electrical resistivity less than or equal to 10Ohm/mm³.